It is desirable to form oil-in-water emulsions, and various techniques have been proposed to accomplish this task.
In the past, oil and polysorbate (or lecithin) and water have been combined to produce an emulsion, but the results have been unsatisfactory. The oil phase separated out of the mixture after relatively short periods of time and off-odors and off-tastes that developed indicated that oxidation products of the oil had formed. Oil and xanthan gum and water mixtures are only temporarily stable, like those found in salad dressings. Emulsification of oil can also be achieved through the addition of water to the oil, combined with strong, lengthy agitation, but the resulting emulsion is very unstable.
Newer approaches have involved the use of proteins as emulsifiers. However, these emulsions are not stable over a wide range of pH conditions. For example, a protein that forms a stable emulsion under low pH conditions (e.g., pH 4) would denature at higher pH (e.g., pH 7), and would no longer act as an emulsifier. Another problem with protein emulsifiers is that upon heating, the protein is destabilized by its conformational change.
The above-described techniques have failed because of the difficulty in maintaining the emulsification and the stability of the oils. The emulsification of the aqueous and oil phases is usually temporary, and the oil/water mixture typically reverts to separate aqueous and oil phases without continued agitation. When the oil is susceptible to oxidation, as is the case with long chain polyunsaturated fatty acids (LCPUFA), stability of the product is also diminished due to the more rapid oxidation of the oils, and in particular, the LCPUFA oils. Protein-based emulsions are not stable over the wide range of pH and temperature conditions found in foods.
It would be advantageous to incorporate LCPUFA-containing oils in aqueous mixtures, such as aqueous food, cosmetic, pharmaceutical and industrial product matrices, without having the oil and water separate into two distinct phases. It would be advantageous to find ways to stabilize an oil-in-water emulsion over a long period of time, in other words, to form an emulsion that is physically stable (e.g., the oil and the water do not phase separate) for at least 30 days. It would be advantageous if the oil is protected by the emulsion from oxidation, in particular, when the oil is susceptible to oxidation, such as a LCPUFA oil.